1. Field of the Invention
The present invention relates generally to radio frequency (RF) devices, and more particularly to inverted F antennas, shield cans and related circuitry and devices.
2. Background of the Invention
Planar inverted F antennas generally include at least one planar radiating element and a ground plane in a plane parallel to the radiating element. A short ground tab typically joins the radiating element to the ground plane. In one known configuration, as exemplified by the structure shown in U.S. Pat. No. 6,218,991 to Sanad, the radiating element is fed via a separate center pin that is located within a periphery of the ground plane. In this design, the short ground tab is also located within the periphery of the ground plane. Also, in Sanad's device, the radiating element, ground plane, center pin and short ground tab are all separate components that must be assembled together.
In another known configuration, like that shown in FIG. 1 of U.S. Pat. No. 6,255,994 to Saito, both a feeding terminal and a grounding terminal are located at one end of the radiating element, are both integral with the radiating element, and are both soldered to a portion of the ground plane. The device shown by Saito also includes a spacer that is disposed between the radiating element and the ground plane. Thus, as exemplified by both the Sanad and Saito devices, inverted F antennas typically comprise several individual parts that must be assembled and soldered together to obtain the desired configuration.
Inverted F antennas, like those mentioned above, are typically used in combination with radio frequency (RF) modules (e.g., transmitter, receivers) that are combined in relatively small packages that enclose, for example, mobile or cordless telephones. Such RF modules are typically encapsulated or substantially surrounded by a shield or shielding can that enables the RF module to operate without interference caused by a local antenna or other close or distant radiation source. A typical shield can 90 mounted to a circuit board is shown in FIG. 9.
Thus, in many devices that employ an inverted F antenna, not only is a ground plane for the inverted F antenna necessary, but there must also be provided a separate shield can for an associated RF module. Designing devices that incorporate both of these elements (ground plane and shield can), however, undesirably increases space requirements for the overall device and package.